A new method has been developed for the construction of alpha,alpha-disubstituted cyclic beta-amino acid derivatives via the sulfanyl radical addition-cyclization reaction of oxime ether connected with acrylate. This reaction proceeded smoothly to give the cyclized products that contained a quaternary carbon center. Furthermore, the use of carbon centered radicals in the reaction allowed for the formation of cyclic amines containing various alkyl chains. The cyclized product with a quaternary carbon center could also be converted to sterically congested cyclic beta-amino acid.